This invention relates to a scroll compressor wherein the housing components are force-fit into the housing cylinder.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In a typical scroll compressor, a pair of scroll members each have a base with a generally spiral wrap extending from the base. One of the two scroll members orbits relative to the other, and the wraps interfit to define compression chambers.
A scroll compressor is typically assembled by preparing a modular "pump unit" which includes the two scroll members and a crank case which supports the orbiting scroll. The pump unit is inserted as a modular preassembled unit into a cylindrical housing. A shaft is then inserted into the pump unit, and supported in a lower bearing.
In the past, pump units have been secured to the cylinders by many different methods. As one example, the pump unit has been welded to the cylinder. Other examples include various bolting arrangements, etc. Similarly, the lower bearing has typically been welded to the cylinder.
These known assemblies have been rather expensive and time consuming. One proposed method has been to force-fit the components into the cylinder. However, the known crankcases and the known lower bearings have been non-continuous at their outer periphery. When these known non-continuous members have been force-fit into the housing, there has thus been force-fit connections at less than the full inner circumference of the housing.
The non-full inner circumference interference fits have caused the shell to take the shape of the inner object, which causes other assembly problems.
Known equations for calculating the holding strength of an interference connection show that a non-continuous member has a much lower holding strength than a generally continuous force-fit member.
In addition, the overall surface contact area between the two members to be held together by an interference fit also effects the holding force. The structure in the prior art compressors which was in contact with the housing have not extended for a long distance, and thus have had relatively small holding areas. Again, this has resulted in undesirably low holding strength.
In the prior art non-continuous force-fit connections, there has not been sufficient holding strength to be practically reliable as the only means of holding the parts. However, these known formulas have never been applied to the concept of interference housing components into scroll compressor cylinders.
In addition, with the prior art, the outer housing did not yield beyond its plastic deformation point. Instead, the housing was able to flow around the spaced contact areas. This also effected the holding force.